Download 1 Division: Cyanobacteria

Brief history of photosynthetic organisms on earth
Division: Cyanobacteria
3.45 bya = Cyanobacteria appear and introduce photosynthesis
blue-green algae
1.5 bya = first Eukaryotes appeared (nuclear envelope and ER
thought to come from invagination of plasma membrane)
0.9 bya = first multicellular algae (Rhodophyta - Red algae)
800 mya = earliest Chlorophyta (Green algae)
400-500 mya = plants on land – derived from Charophyceae
250 mya = earliest Heterokontophyta (Brown algae)
100 mya = earliest seagrasses (angiosperms)
• Single class: Cyanophyceae
• ~150 genera
• ~4037 species
1
Groups (Kingdom)
DOMAIN
1.Bacteria- cyanobacteria (blue green algae)
2.Archae
3.Eukaryotes
1. Alveolates- dinoflagellates
2
Domain Bacteria- unicellular, lacking a nucleus, ribosomes, tRNA,
peptoglycan in the cell wall
Phylum Low-GC Gram-positive- staph infections & antrax
Phylum High GC- Gram-positive- tuberculosis & antibiotics
Phylum Hyperthermophilic bacteria- live at high temperatures
Phylum Hadobacteria-live at high temps, consume nuclear waste
Phylum Cyanobacteria- blue green algae, origin of the chloroplast
Phylum Spirochetes- syphilis & lime disease
Phylum Chlamydias- intercellular parasites
Phylum Proteobacteria- pathogens, nitrogen fixers, autotrophs,
origin of mitochondria
2. Stramenopiles- diatoms, heterokonyophyta
3. Rhizaria- unicellular amoeboids
4. Excavates- unicellular flagellates
5. Plantae- rhodophyta, chlorophyta, seagrasses
6. Amoebozoans- slimemolds
7. Fungi- heterotrophs with extracellular digestion
8. Choanoflagellates- unicellular
9. Animals- multicellular heterotrophs
3
4
1
Cyanobacteria Cellular Structure:
Cyanobacteria are important because:
•Nucleus?
• Cyanobacteria are modern representatives of the very
first photosynthetic organisms on Earth.
•Chloroplasts?
•First organisms to have 2 photosystems and to produce
organic material and to give off O 2 as a biproduct.
• Pigments?
•Instrumental in transforming early earths atmosphere
to an oxidizing one  the oxygen revolution
• Carbon storage?
• Most common algal group in terrestrial systems and
symbiotic relationships
• Flagella?
5
Cyanobacteria Cellular Structure
6
Cellular Structure: microscopic
No complex organelles
• Unicells in mucus envelope
Thyllakoids- photosystems I & II
Carboxisomes- bacterial microcompartments that contain enzymes
involved in carbon fixation
- concentrate CO2 for RuBisCo
• Colonies
• Filaments, Branched filaments most complicated form
7
8
2
Cyanophyta Cellular Structure
vegetative cells- photsynthesize
“facultative chemoautotropes”
spores- resting stages
•Many spp have the ability to photosynthesize under both aerobic
and anaerobic conditions
heterocysts- specialized cells for fixing nitrogen
Difference is where the electrons come from:
Aerobic conditions? Electron donor is Water O2 produced
C0 2 + H2 0
CH2 O + O2
Anaerobic conditions? Electron donor is Hydrogen sulfide  Water is produced
2H2 S + CO2
CH2 O + 2S + H2 O
9
Morphology of Cyanophyta
• Cell wall made of peptidoglycan, polymer consisting of sugars and
amino acids (not cellulose), similar to gram-negative bacteria
• Trichome- Row of cells
• Filament- Trichome within a mucilaginous sheath
10
Mucilaginous Sheath –
–motion (gliding)
-protection against desiccation
- protection against UV irradiance
Sheath is often colored:
Red = acidic
Blue = basic
Yellow/Brown = high salt
• Mucilaginous Sheath- layer of mucilage outside of cell wall
• Possible to have > 1 trichome within a filament
11
12
3
False branching =
True branching =
outgrowth of filaments
adjacent to dead or
specialized cells; filament
curves
outgrowth from cells that
change their axis of
division, 90 degrees from
axis of trichome
Movement
1.
”Gliding” against a solid substrate -no change in shape or obvious
pushing; no ability to steer, sometimes trichome rotates within
sheath, and sheath is left behind as the trichome moves forward
2. Jet propulsion = excrete mucus
3. Helical species (e.g. Spirulina), use waves of contraction
4. Swimming? No idea how they do this, but evidence of
chemotaxis and phototaxis.
5. Changing buoyancy
13
Buoyancy:
14
Reproduction:
Cells contain gas vesicles or gas vacuole
= hollow cylinders made of protein
•low light? Decreased Ps  metabolism of polysaccharides 
increase in gas vacuoles  float upward
•high light? Increased Ps  Accumulation of polysaccharides 
cell pressure increases  gas vacuoles shrink  sink
 No sexual reproduction  some DNA transfer has been
observed, not conjugation per se.
 Asexual reproduction through:
1-Binary fission – dividing in two
2-Fragmentation of colonies
3-Endospores/exospores
4-Hormogonia
5-Akinetes
15
16
4
Reproduction
Asexual Reproduction
Hormogonia – short piece of trichome
found in filaments. It detaches from
parent filament and glides away
4. Hormogonia = short piece of trichome that detaches
from parent filament and glides away
Separation disk or “Necridium” = funky dead cell
where detachment occurs
17
18
Hormogonia
Reproduction
Akinete
5. Akinetes = thick-walled resting spores.
Packed with energy reserves; dense = sink to the bottom
when released.
Triggered by unfavorable conditions, can remain viable
for years.
H
19
A - akinete
20
5
Earliest evidence of Cyanobacteria comes from stromatolites:
Precambrian- 3.5 BYA
Wide Range of Habitats
•Freshwater lakes
•Terrestrial soils
hotsprings at Yellowstone Park
• Marine systems (intertidal, open ocean)
• Extreme environments (e.g. salt flats, hot springs, glaciers, etc.)
• Endosymbiotic: diatoms, sponges, tunicates, lichens, polar bear
fur, bryophytes, gymnosperms, angiosperms
21
Stromatolites
• Stromatolites are produced by successive deposition
through “grain trapping” or calcification:
• Mucilaginous sheath of cyanos physically blocks the
movement coarse gain sediments and laminates it to
the surface of the stromatolite
• Attract and bind Ca ions to negatively charged sites
• Locations : hypersaline seas (Shark Bay,western Aus.),
frozen lakes (Antarctic), hot springs (Yellowstone), the
Caribbean
•Most cyano’s active during the day= layers count the
numbers of days
•Also they grow up toward the sun and are directional
toward the sun (=can document annual motion of sun)
23
• Layered calcareous mounds that contain fossils of cyanobacteria that
look like Oscillatoria
22
Another big reason Cyanobacteria are cool and
ecologically important: Nitrogen fixation
Many are able to fix nitrogen = convert atmospheric N2 (N
N)
to a usable form (Ammonium: NH 4 +) using enzyme nitrogenase
N can be limiting; necessary for the production of amino acids
Only cyanobacteria and proteobacteria can fix N;
BUT cyanobacteria also produce O2 during photosynthesis
This is a trick, because O2 inactivates nitrogenase
How do they do it???
24
6
1. Spatial separation of functions:
2. Temporal separation of functions:
Heterocyst = special cells for N fixation.
•
• Thick-walled, and larger
than other vegetative cells;
hollow looking
Fix N in the dark, Ps in the daytime;
Every N-fixing cyanobacteria fits into these two
categories except:
Trichodesmium = marine, colonial species; fix nitrogen
under aerobic conditions in the light through division of
• Not capable of dividing
labor among cells within a filament (no heterocysts)!
• Not photosynthetic, so no
CO2 fixation or O2 production
• Microplasmedesmat a
connect to other cells in
filament
25
26
Domain Bacteria- unicellular, lacking a nucleus, ribosomes, tRNA,
peptoglycan in the cell wall
The dark side of cyanobacteria?
Phylum Cyanobacteria- 4037 species
Class Cyanophyceae- 4037 species, 7 orders
Cyanobacterial blooms = death and destruction
Swimmer’s itch = Lyngbia  releases chemicals
Order Chroococcales- 954 species
filamentous, no specialized structures
Cyanotoxins: released by animal ingestion  neurotoxins (e.g.
Anabaena, Oscillatoria ) and hepatotoxins (e.g. Microcystis,
Nostoc ) (death to mammals, birds, fishes , no known human
deaths)
Order Oscillatoriales –926 species
filamentous, no specialized structures
Order Nostocales- 1,297 species
filamentous, specialized structures,
may have true branching
Oscillatoria
27
28
7
Order Chroococcales
Genus Spirulina
Domain Bacteria- unicellular, lacking a nucleus, ribosomes, tRNA,
peptoglycan in the cell wall
• Filament is spiral
•Major food source for flamingos
• Commercial food source
• No heterocysts or akinetes
Phylum Cyanobacteria- blue green algae, origin of the chloroplast
• benthic or plantonic, freshwater, thermal
& mineral springs, coastal & brackish waters
• 52 species
Class CyanophyceaeOrder Chroococcales- filamentous, no specialized structures
Order Oscillatoriales -filamentous, no specialized structures
Order Nostocales- filamentous, specialized structures,
may have true branching
29
Order Oscillatoriales
Order Oscillatoriales
Genus Oscillatoria
30
- Unbranched filaments
-No readily identifiable sheath, but is present
-No specialized cells
-Fix nitrogen
-Early precambrian fossil stromatolites
-Planktonic, form mats on mud, stone, sand, in
freshwater, brachish, marine
-137 species
31
GenusTrichodesmium
- Important marine N fixer
- Segregates N fixing within colonies
(lacks heterocysts)
- More Phycoerythrin than Phycocyanin
 Red color, gave the Red Sea its name
- Strictly planktonic- marine & fresh water
-10 species
32
8
Domain Bacteria- unicellular, lacking a nucleus, ribosomes, tRNA,
peptoglycan in the cell wall
Phylum Cyanobacteria- blue green algae, origin of the chloroplast
Class Cyanophyceae-
Order Nostocales
Genus Nostoc
Order Chroococcales- filamentous, no specialized structures
• Fixes nitrogen
• Has heterocysts in the middle of
filaments
•Akinates midway between heterocysts
•94 species
•Freshwater
Order Oscillatoriales -filamentous, no specialized structures
Order Nostocales- filamentous, specialized structures,
may have true branching
33
Order Nostocales
Genus Anabaena
34
Order Nostocales
• Produces neurotoxins that become release
when they are ingested by animals
• Fixes nitrogen
• Has heterocysts in the middle of filaments
• Akinates adjacent to heterocysts
• Planktonic, or periphytic, benthic, soils,
• 117 species
35
Genus Calothrix
• Fixes nitrogen
• Has heterocysts, often at the
base of filaments
• Filaments taper at ends
• Periphytic on algae, aquatic plants,
stone, wood, high intertidal
•132 species
36
9
Order Nostocales
Cylindrospermum
Order Nostocales
• Produces neurotoxins that are
released when they are ingested.
• Fixes nitrogen
• Has heterocyst at the base of
large akinetes
•Periphytic or soils
•49 species
37
GenusTolypothrix
• Fixes nitrogen
• Has heterocysts
• Exhibits false branching
• 60 species
•Mainly submerged, also aerophytic
habitats
38
Order Nostocales
Stigonema
- Has heterocysts
- Exhibits True Branching
- Often found as phycobiont in lichens,
terrestrial & soil, freshwater
- 62 species
39
10